x86: remove unnecessary memset()

No need to clear the memory allocated by alloc_bootmem().
It is already filled with zero.
Signed-off-by: NAkinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/io_apic_64.c

@@ -2315,7 +2315,6 @@ static struct resource * __init ioapic_setup_resources(void)
 	res = (void *)mem;
 
 	if (mem != NULL) {
-		memset(mem, 0, n);
 		mem += sizeof(struct resource) * nr_ioapics;
 
 		for (i = 0; i < nr_ioapics; i++) {